A little while back, Behavioral and Brain Sciences showcased a paper arguing that quantum probabilities might be useful for cognitive modeling. I still haven’t read more than a bit of the beginning, but it being in BBS means that it can’t be entirely bad.
Do note that they explicitly do not suggest that quantum mechanics would have anything to do with the way the brain functions:
We note that this article is not about the application of quantum physics to brain physiology. This is a controversial issue (Hammeroff 2007; Litt et al. 2006) about which we are agnostic. Rather, we are interested in QP theory as a mathematical framework for cognitive modeling. QP theory is potentially relevant in any behavioral situation that involves uncertainty. For
example, Moore (2002) reported that the likelihood of a “yes” response to the questions “Is Gore honest?” and “Is Clinton honest?” depends on the relative order of the questions. We will subsequently discuss how QP principles can provide a simple and intuitive account for this and a range of other findings.
Rather, they take the general mathematical framework of quantum probability and apply it to cognitive phenomena:
But what are the features of quantum theory that
make it a promising framework for understanding cognition? It seems essential to address this question before
expecting readers to invest the time for understanding
the (relatively) new mathematics of QP theory.
Superposition, entanglement, incompatibility, and interference are all related aspects of QP theory, which endow
it with a unique character. Consider a cognitive system,
which concerns the cognitive representation of some information about the world (e.g., the story about the hypothetical Linda, used in Tversky and Kahneman’s [1983] famous
experiment; sect. 3.1 in this article). Questions posed to
such systems (“Is Linda feminist?”) can have different outcomes (e.g.,“Yes, Linda is feminist”). Superposition has to
do with the nature of uncertainty about question outcomes.
The classical notion of uncertainty concerns our lack of
knowledge about the state of the system that determines
question outcomes. In QP theory, there is a deeper
notion of uncertainty that arises when a cognitive system
is in a superposition among different possible outcomes.
Such a state is not consistent with any single possible
outcome (that this is the case is not obvious; this remarkable
property follows from the Kochen–Specker theorem).
Rather, there is a potentiality (Isham 1989, p. 153) for
different possible outcomes, and if the cognitive system
evolves in time, so does the potentiality for each possibility.
In quantum physics, superposition appears puzzling: what
does it mean for a particle to have a potentiality for different
positions, without it actually existing at any particular position? By contrast, in psychology, superposition appears an
intuitive way to characterize the fuzziness (the conflict,
ambiguity, and ambivalence) of everyday thought.
Entanglement concerns the compositionality of complex
cognitive systems. QP theory allows the specification of
entangled systems for which it is not possible to specify a
joint probability distribution from the probability distributions of the constituent parts. In other words, in entangled
composite systems, a change in one constituent part of the
system necessitates changes in another part. This can lead
to interdependencies among the constituent parts not possible in classical theory, and surprising predictions, especially
when the parts are spatially or temporally separated.
In quantum theory, there is a fundamental distinction
between compatible and incompatible questions for a cognitive system. Note that the terms compatible and incompatible have a specific, technical meaning in QP theory, which
should not be confused with their lay use in language. If
two questions, A and B, about a system are compatible, it
is always possible to define the conjunction between A
and B. In classical systems, it is assumed by default that
all questions are compatible. Therefore, for example, the
conjunctive question “are A and B true” always has a yes
or no answer and the order between questions A and B
in the conjunction does not matter. By contrast, in QP
theory, if two questions A and B are incompatible, it is
impossible to define a single question regarding their conjunction. This is because an answer to question A implies a
superposition state regarding question B (e.g., if A is true at
a time point, then B can be neither true nor false at the
same time point). Instead, QP defines conjunction between
incompatible questions in a sequential way, such as
“A and then B.” Crucially, the outcome of question A can affect the
consideration of question B, so that interference and order
effects can arise. This is a novel way to think of probability,
and one that is key to some of the most puzzling predictions
of quantum physics. For example, knowledge of the position of a particle imposes uncertainty on its momentum.
However, incompatibility may make more sense when considering cognitive systems and, in fact, it was first introduced in psychology. The physicist Niels Bohr borrowed
the notion of incompatibility from the work of William
James. For example, answering one attitude question can
interfere with answers to subsequent questions (if they
are incompatible), so that their relative order becomes
important. Human judgment and preference often
display order and context effects, and we shall argue that
in such cases quantum theory provides a natural explanation of cognitive process.
“Quantum probability” in this case should really be called “noncommutative probability”: that emphasizes that there’s no direct connection to quantum mechanics as a physical theory. The basic mathematical feature is that random variables don’t commute.
A little while back, Behavioral and Brain Sciences showcased a paper arguing that quantum probabilities might be useful for cognitive modeling. I still haven’t read more than a bit of the beginning, but it being in BBS means that it can’t be entirely bad.
Do note that they explicitly do not suggest that quantum mechanics would have anything to do with the way the brain functions:
Rather, they take the general mathematical framework of quantum probability and apply it to cognitive phenomena:
“Quantum probability” in this case should really be called “noncommutative probability”: that emphasizes that there’s no direct connection to quantum mechanics as a physical theory. The basic mathematical feature is that random variables don’t commute.
Live and learn.